Method of reinforcing opening of steel frame girder

ABSTRACT

A tube is inserted in an opening of a girder web. Grooves formed in edges of the opening are mated with grooves on the tube, and a pair of reinforcing plates are attached to the tube so as to sandwhich the girder web. An auxiliary force applicator is inserted in an axial force introduction hole of the reinforcing plates, and in a state where one reinforcing plate is fixed, a load is applied to the other reinforcing plate in the rotational axial force direction, and as it is rotated greater force is applied, and the girder web and the pair of reinforcing plates are friction grip connected. The auxiliary force applicators are pulled out from the axial force introduction holes and the axial holes are plug welded, further fixing the reinforcing plates and the girder web.

FIELD OF THE INVENTION

The present invention relates to a method for reinforcing an opening of a steel frame girder.

BACKGROUND OF THE INVENTION

Generally, a girder web of a steel frame girder is configured such that a through hole is provided for various types of piping and wiring, and in this girder web opening, reinforcing means for compensating for the cross-sectional lack of material in such opening is provided. Such reinforcing means for a girder web opening includes a ring-shaped reinforcing plate (for example, see Laid-Open Japanese Patent Application No. H7-238635). This Laid-Open Japanese Patent Application discloses technology such that, as shown in FIG. 13, a male screw-attached tube 52 a protrudingly provided in a central hole of a ring-shaped reinforcing plate 52 is inserted in a web opening 51 of a steel frame girder 50, a female screw-attached tube 53 a protrudingly provided in a central hole of the other ring-shaped reinforcing plate 53 is inserted in the web opening 51 from the other side, mating with the male screw-attached tube 52 a, thus tightening both reinforcing plates 52, 53 to the surfaces of the web opening part 51 of the steel frame girder 50, sandwiching and reinforcing the same.

However, the shapes of the reinforcing plates 52, 53 described in the Laid-Open Patent Application are complicated. Further, simultaneously fitting the reinforcing plates 52, 53 and a washer 54 is difficult for a single worker, requiring at least two persons including one in front of and one behind the girder. Further, depending on girder web thickness, the fixed length of the female screw-attached tube 53 a, male screw-attached tube 52 a length and washer 54 means that the reinforcement range is limited. If all girder webs are to be reinforced, reinforcing plates 52, 53 with female screw-attached tubes 53 a and male screw-attached tubes 52 a of differing length must be prepared.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide a method for reinforcing a steel frame girder opening that increases freedom of design and construction method, and provides a greater reinforcement effect in a manner that is simple and safe in terms of structural reliability.

Thus, a first aspect of the present invention is a steel frame girder opening reinforcement method characterized by the fact that a central tube having screw grooves formed on the outer surface thereof is inserted in an opening provided in a girder web for a steel frame girder, screw grooves formed in the edges of openings in a pair of reinforcing bodies are mated with the screw grooves of the central tube from the respective outward directions so as to sandwich the girder web therebetween, and the girder web and the pair of reinforcing bodies are friction grip connected and fixed.

A second aspect of the present invention is a steel frame girder opening reinforcement method characterized by the fact that a central tube having screw grooves formed on the outer surface thereof is inserted in an opening provided in a girder web for a steel frame girder, and screw grooves formed in edges of openings of a pair of reinforcing bodies are mated with the screw grooves of the central tube from the respective outward directions so as to fix the girder web and the pair of reinforcing bodies.

A third aspect of the present invention is a steel frame girder opening reinforcement method according to the first or second aspect characterized by the fact that, after the girder web and the pair of reinforcing bodies are fixed, the girder web and the pair of reinforcing bodies are partially welded, so that the girder web and the pair of reinforcing bodies are partially fixed by welding.

A fourth aspect of the present invention is a steel frame girder opening reinforcement method according to the first or second aspect characterized by the fact that rotational force is applied to axial force introduction holes provided in the pair of reinforcing bodies, thereby fixing the girder web and the pair of reinforcing bodies.

A fifth aspect of the present invention is a steel frame girder opening reinforcement method according to the fourth aspect characterized by the fact that, after rotational force is applied to the axial force introduction hole, fixing the girder web and the pair of reinforcing bodies, the axial force introduction holes are filled by welding, thereby weld fixing the reinforcing bodies and the girder web.

A sixth aspect of the present invention is a steel frame girder opening reinforcement method according to the first, second or third aspect characterized by the fact that after the girder web and the pair of reinforcing bodies are fixed, the girder web and the pair of reinforcing bodies are further fixed by bolts inserted therein and nuts.

A seventh aspect of the present invention is a steel frame girder opening reinforcement method according to the first or second aspect characterized by the fact that the screw grooves of the central tube are mated with screw grooves formed on the inner surface of a sleeve tube for a steel framed reinforced concrete structure.

An eighth aspect of the present invention is characterized by the fact a central tube is inserted in an opening provided in a girder web of a steel frame girder, and the girder web and the pair of reinforcing bodies are fixed in a state where the girder web is sandwiched by the pair of reinforcing bodies from the respective outward directions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional front view of a steel frame girder in a reinforced state;

FIG. 2 is a side view of a steel frame girder in a reinforced state;

FIG. 3 is a vertical cross-sectional front view of a steel frame girder in a reinforced state with a sleeve tube attached thereto;

FIG. 4 is a drawing illustrating a reinforcing steel plate;

FIG. 5 is a vertical cross-sectional view of a central tube;

FIG. 6 is a vertical cross-sectional view of a sleeve tube;

FIG. 7 is a side view of a steel frame girder in a reinforced state illustrating another embodiment;

FIG. 8 is a cross-sectional view along the X-X line of FIG. 7;

FIG. 9 is a side view of a reinforcing steel plate for explaining the operational principles of another embodiment;

FIG. 10 is a schematic view of application of force when a strength test is performed;

FIG. 11 is an M-R skeleton curve diagram of test results;

FIG. 12 is a front view of a steel frame girder in a reinforced state showing a third embodiment of the present invention; and

FIG. 13(A) is a side view illustrating conventional art, FIG. 13(B) is a cross-sectional view along the A-A line of FIG. 13(A), and FIG. 13(C) is an enlarged view of section B of FIG. 13(B).

DETAILED DESCRIPTION

The first embodiment of the present invention will be explained with reference to FIGS. 1 through 6. First, in an intermediate portion of a girder web 1A of a steel frame girder 1 that has an H-shaped cross section and is the base metal to be reinforced, a circular opening 1B is provided. The reinforcement operation is carried out with the steel frame girder 1 not lying down but upright, by insertion of a hollow cylindrical central tube 3 having screw grooves 3A formed on the full length of the outer surface thereof (see FIG. 5) into an opening 1B of the girder web 1A.

Next, a pair of reinforcing steel plates 2, 2 having a circular opening formed in the center thereof (see FIG. 4) are attached by mating screw grooves 2A formed in the edges of the opening thereof with the screw grooves 3A of the central tube 3 from the respective outward directions so as to sandwich the girder web 1A therebetween.

Then, in a plurality of axial force introduction holes 5, 5 (for example, four, one every 90 degrees) provided in the reinforcing steel plates 2, 2, auxiliary force applicators such as jigs are inserted, and in a state where one reinforcing steel plate 2 is fixed, a load is applied on the other reinforcing steel plate 2 in the rotational axial force direction, causing rotation thereof, by which an even larger force is applied. In this case, a large force is applied until friction force arising between the girder web 1A and the pair of reinforcing steel plates 2, 2 causes transfer of stress, resulting in a friction grip connection. A friction grip connection in this case is insufficient if the pair of reinforcing steel plates 2, 2 are only tightened manually onto the girder web 1A, as described above, so they are further tightened up by using jigs or the like.

When large force as described above has been applied, the auxiliary force applicators such as jigs are pulled out from the axial force introduction holes 5, and the axial force introduction holes 5 are filled by plug welding, thereby securely fixing the reinforcing steel plates 2, 2 and the girder web 1A, and preventing the reinforcing steel plates 2, 2 from loosening, sliding or peeling off.

The reinforcing steel plates 2, 2 are even more effective if pretreated with blast, red rust or the like on the side that is attached to the girder web 1A of the steel frame girder 1 so that stronger friction arises.

Next, with reference to FIG. 3, explanation will be made for the case of a girder of a steel framed reinforced concrete structure (SRC). The screw grooves 3A formed on the outer surface of the central tube 3 used when fitting the reinforcing steel plates 2, 2 in FIGS. 1 and 2 are mated with the screw grooves 4A formed on the inner surface of the respective ends of hollow cylindrical sleeve tubes 4, 4 as illustrated in FIG. 6, thereby attaching the sleeve tubes 4, 4 to the respective ends of the central tube 3.

Because the screw grooves 4A are formed on the inside of the sleeve tubes 4, 4, it is easy to achieve a desired length after fitting. Further, the sleeve tubes need not be assembled at the manufacturing plant, but assembled at the construction site to facilitate transport.

In case of the friction grip connection of the first embodiment, the reinforcing steel plates 2, 2 and the girder web 1A can be tightly fixed, without necessarily requiring plug welding in order to improve reinforcing effects.

Next, a second embodiment of the present invention will be explained with reference to FIGS. 7 through 9. First, in an intermediate portion of a girder web 11A of a steel frame girder 11 that has an H-shaped cross section and is a base metal to be reinforced, a circular opening 11B is provided. The reinforcement operation is carried out with the steel frame girder 11 not lying down but upright, and a hollow cylindrical central tube 13 on which screw grooves 13A are formed on the full length of the outer surface is inserted in an opening 11B of the girder web 11A. Next, a pair of reinforcing steel plates 12, 12 having a circular opening formed in the center thereof are attached by mating screw grooves 12A formed in the edge of the opening with the screw grooves 13A of the central tube 13 from the respective outward directions so as to sandwich the girder web 1 IA therebetween.

Thereafter, in a plurality of axial force introduction holes 15, 15 (for example, four, one every 90 degrees) provided in the reinforcing steel plates 12, 12, auxiliary force applicators such as jigs are inserted, and in a state where one reinforcing steel plate 12 is fixed, load is applied to the other reinforcing steel plate 12 in the rotational axial force direction, and force is applied by manual tightening by a worker.

In this case, without using-jigs or the like, a worker may by manual tightening directly fix a pair of reinforcing steel plates 12, 12 to the girder web 11A so as to sandwich the girder web 11A therebetween. In either case, a pair of reinforcing steel plates 12, 12 and the girder web 11A are fixed to each other with no gap therebetween.

Further, even when jigs or tightening mechanisms are used, before friction grip connection of the girder web 11A and the pair of reinforcing steel plates 12, 12, application of rotation-causing force is stopped. After application of this rotational force is stopped, to improve the reinforcing effect, the axial force introduction holes 15 serve as plug welds 20, 21, thereby securely fixing the reinforcing steel plates 12, 12 and the girder web 11A.

FIG. 9 is a side view for explaining operating principles of this embodiment. Explanation will be made of operation in a case where external force is applied to the steel frame girder web 11A. First, at section A where the screw grooves 12A of the reinforcing steel plates 12, 12 mate with the screw grooves 13A of the central tube 13, the reinforcing steel plates 12, 12 sandwich the girder web 11A from the front and back, and together with the central tube 13 are fixed to the girder web 11A.

As external force grows larger, the out-of-plane deformation of the girder web 11A also grows larger; however, the pair of reinforcing steel plates 12, 12 are fixed to the girder web 11A, inhibiting deformation of the girder web 11A.

Further, as the girder web 11A is partially welded to the reinforcing steel plates 12, 12 by the plug welds 20 (on one reinforcing steel plate 12 side) and the plug welds 21 (on the other reinforcing steel plate 12 side), on sections B and C, the reinforcing steel plates 12, 12 and the girder web 11A are made unitary, inhibiting deformation of the girder web 11A and giving rise to large reinforcing effects.

Further, because at section A where the screw grooves 12A of the reinforcing steel plates 12, 12 mate with the screw grooves 13A of the central tube 13, the central tube 13 provided in the center of the opening 11B inhibits three-dimensional torsion of the girder web 11A at places other than the reinforcing steel plates 12, 12, and plastic deformation capacity is markedly improved.

A strength test was performed by using a loading test device as illustrated in FIG. 10, and the results are as indicated in the M-R skeleton curve diagram of FIG. 11. F and G of FIG. 11 indicate steel frame girders on which the reinforcing method of the present embodiment was implemented. For the purpose of comparison with the present embodiment, D indicates a steel frame girder without an opening, and E indicates a non-reinforced steel frame girder with an opening.

In this case, a horizontal load was repeatedly applied to the girder top; for the girder without an opening D and the non-reinforced girder with an opening E, this was carried out until ultimate strength in the positive direction was reached and for the 9 mm-thick reinforcing steel plate F and the 12 mm-thick reinforcing steel plate G, this was carried out until angle of rotation reached 1/10.

Using the reinforcing method of the present embodiment, strength was restored. In particular, it was confirmed that effects on maximum strength were large and the decline of strength after the maximum strength was gradual, confirming that ultimate strength was significantly improved.

More specifically, as can be seen from the strength test results, when the present reinforcing method is carried out, the steel frame girders F and G of the present embodiment have far greater deformation capacity than the girder without an opening D. Under current standards, earthquake resistance design relies on building ductibility, and the preferred structural design uses as a total yield mechanism a type where girders yield first at time of a large earthquake. Thus, sufficient ductibility is required at sections of a girder end where a hinge is to be formed. As shown in the strength test results, the present reinforcing method has plastic deformation capacity greater than that of the girder without an opening D (i.e., when the girder is used in a normal state). And it was greatly improved when compared to the deformation capacity of the non-reinforced girder E with an opening.

For the above reasons, because use of the present reinforcing method in sections of girder ends where plasticity hinges are to be formed improves a structure's earthquake resistance, there is increased freedom of design, allowing for reduction of steel frame girder size or widening of the distance between columns. This should help realize designs for steel structures based on concepts completely different from conventional methods.

In the second embodiment, a sleeve tube for a steel framed reinforced concrete structure (not shown in the drawing) may be fitted, as in the first embodiment, by mating the screw grooves 13A of the central tube 13 with screw grooves formed on the internal surface of an end portion thereof. In this way, in both the first and second embodiments, the sleeve tube can be attached by using the screw grooves of the surplus portion of the central tube, and the length to the sleeve tube end portion (from the girder web) at the time of attachment can be adjusted even without relying on erection accuracy, eliminating such problems as its being longer or shorter than the concrete frame. Further, there is no need to attach sleeve tubes to steel frame girders at a manufacturing plant prior to transport, improving load rate of a transport vehicle.

As described above, a girder web of a steel frame girder and reinforcing steel plates are fixed by either the connection of the first embodiment, which constitutes a friction grip, or the connection of the second embodiment, which does not reach the degree of a friction grip, and are further fixed by plug welding the axial force introduction holes of the reinforcing steel plates. As an alternative to plug welding, through holes may be provided in both reinforcing steel plates and the girder web, and both reinforcing steel plates and the girder web fixed by bolts inserted therein and nuts, enabling selection of fixing method in accordance with working environment.

In this case, the through holes are provided in the girder web and at positions on one reinforcing steel plate corresponding to the axial force introduction holes (or other separately formed through hole) of the other reinforcing steel plate, and the bolts are inserted in the axial force introduction holes of the other reinforcing steel plate and the through holes of the girder web and the one reinforcing steel plate and are fixed with nuts. The fixing is carried out at least at two sections symmetrical with each other across the center of the reinforcing steel plate therebetween. Therefore, the reinforcing steel plates and the girder web are fixed with little or no plug welding, thus having little thermal impact on the girder web and inhibiting or preventing deformation or warpage of a steel frame girder by welding heat.

No requirement is made with respect to fixing the reinforcing steel plates and the girder web by plug welding the axial force introduction holes of the reinforcing steel plates. Alternatively, the outer edges of a pair of reinforcing steel plates and a girder web may be fillet welded.

Further, screw grooves are formed across a prescribed range of the outer surface of the central tube, for example, across as a wide range as possible or across the full length, enabling reinforcement of girder webs with different thicknesses with a single type of reinforcing steel plate, without the need to prepare multiple kinds.

Further, the pair of reinforcing bodies may be fitted to a girder web so as to sandwich the girder web therebetween, in a state where the central tube has been inserted in the opening of the girder web; alternatively, the girder web and the pair reinforcing steel plates may be fixed such that a central tube in a state where one reinforcing steel plate is fitted thereupon is inserted in the opening, and the other reinforcing steel plate has been fitted from the other side so as to sandwich the girder web therebetween. In the latter case, a single operator can carry out the attaching work.

A third embodiment of the present invention will be explained with reference to FIG. 12. First, in an intermediate portion of a girder web 31A of a steel frame girder 31 that has an H-shaped cross section and is a base metal to be reinforced, a circular opening 31B is provided. Reinforcement operation is carried out with the steel frame girder 31 not lying down but upright, and a hollow central tube 33 is inserted in an opening 31B of the girder web 31A. Next, a pair of reinforcing steel plates 32, 32 having a circular opening formed in the center thereof are disposed so as to sandwich the girder web 31A therebetween.

In this case, the reinforcing steel plates 32, 32 are disposed to sandwich the girder web 31A therebetween so that the central tube 33 inserted in the opening 31B of the girder web 31A engages with the interior of the openings of the pair of reinforcing steel plates 32, 32.

Thereafter, the outer edge of the central tube 33 and the edge of the opening of the reinforcing steel plates 32, 32 are partially welded 35 (at several locations), thereby partially weld fixing the central tube 33 and the reinforcing steel plates 32, 32. This securely fixes the girder web 31A and the pair of reinforcing steel plates 32, 32. Therefore, with the third embodiment as well, the various effects as described above can be obtained. As an alternative to the welding 35, an adhesive may be used for fixing.

The reinforcing steel plates in all the embodiments may be made by casting or forging, but as such methods present problems such as high costs, the plates may be made from rolled steel plates. Further, the shape of a reinforcing steel plate is not limited to circular, and may be polygonal or otherwise shaped. Further, it does not have to be a plate material.

As described above, the present invention provides a method for reinforcing a steel frame girder opening, that increases freedom of design and construction method, and provides a greater reinforcement effect in a manner that is simple and safe in terms of structural realiability. Further, in a case where a central tube in a state where one reinforcing body is fitted thereto is inserted in an opening provided in a girder web of a steel frame girder and the other reinforcing body is fitted from the other side so as to sandwich the girder web therebetween, a single worker can perform the attaching operation. Further, screw grooves are formed across a prescribed range of the outer surface of the central tube, enabling reinforcement of a girder webs with different thicknesses with a single type of reinforcing steel plate, without the need to prepare multiple kinds. 

1. A method of reinforcing an opening in a girder web comprising: inserting a tube on which grooves are formed on the outer surface thereof in an opening provided in a girder web; and mating grooves formed in edges of openings of at least one reinforcing body with the grooves of the tube so as to fix the girder web and the at least one reinforcing body.
 2. The method according to claim 1, wherein the at least one reinforcing body comprises a pair of reinforcing bodies, the girder web being sandwiched between the pair of reinforcing bodies.
 3. The method according to claim 1, wherein the girder web and the at least one reinforcing body are fixed by being friction grip connected.
 4. The method according to claim 1, further comprising partially welding the girder web and the at least one reinforcing body.
 5. The method according to claim 1, wherein rotational force is applied to axial force introduction holes provided in the at least one reinforcing body, thereby fixing the girder web and the at least one reinforcing body.
 6. The method according to claim 5, further comprising plug welding the axial force introduction holes, thereby weld fixing the at least one reinforcing body and the girder web.
 7. The method according to claim 1, further comprising further fixing the girder web and the at least one reinforcing body by bolts and nuts.
 8. The method according to claim 4, further comprising further fixing the girder web and the at least one reinforcing body by bolts and nuts.
 9. The method according to claim 1, further comprising mating the grooves of the tube with grooves formed on the inner surface of at least one sleeve tube.
 10. A method of reinforcing an opening in a girder web comprising: inserting a tube in an opening provided in a girder web; and fixing the girder web and at least one reinforcing body.
 11. The method according to claim 10, wherein the at least one reinforcing body comprises a pair of reinforcing bodies, the girder web being sandwiched between the pair of reinforcing bodies. 